1. Technical Field of the Invention
This invention relates to colorimeters, and more particularly to colorimeters capable of measurement of emitted light from sources that are temporally active.
2. Background Art
The measurement of color is a complex task. The complexity arises from the need to correlate the measurements made by an instrument with the impressions or sensations perceived by the human observer. Much of the prior art is devoted to instrument design that accomplishes the task within the framework of the known requirements for scenes that are continuously illuminated for sources which do not vary over time.
When light sources are temporally variant, and their effects are to measured relative to human responses, it is necessary to carefully separate artifacts that may be detected by the instrument from artifacts which affect the human perception. One method of elimination of temporal variation is to electronically filter the variation out using well known electrical and analytical techniques. The problem with this technique is that it increases measurement times. This increase in measurement time may be a problem in industrial applications which require that measurement times be short.
Automated adjustment and calibration of a CRT while on the assembly line is a typical task which requires minimal measurement time. The monitor adjustments must be servoed by the measurement device and the time of measurement must be short. The monitor is essentially a flashing source, and if the colorimeter is not properly synchronized with the vertical refresh rate of the monitor, the measurements will be very unreliable.
Another typical application is colorimetric analysis of colors on web presses during the production run of a newspaper or magazine. In situations like this it is often useful to use a strobe illuminator to "freeze" the movement of the web. This is done by flashing a source for a very short period. This flash effectively acts as shutter.
Yet another application of this technology is in the automatic calibration of hardcopy within a color copier. A test pattern is printed and examined by the sensor while still in the copier. Colorimeteric information is collected and sent back to a calibration subsystem to adjust the color balance of the media.